Air heater



May 19, 1931.

v. ZICARACRISTI AIR HEATER Filed May 8, 1925' v Patented May 19, 1931 PATENT orrlcs VIBBINIUSZ. CABAOBIB'II, OI snoux vm, NEW YQBK are nm'rna Application filed May 8,

, My invention relates to air heaters of the type that are used in connection with stoker furnaces for utilizing a substantial portion of the heat of the waste gases of combustion to heat air and to direct the heated air into the furnace to support combustion. Air heaters of this type are commonly made up of a pluralit of air heating elements that are arranged si e by side and spaced apart so as it to provide gas passes betweenthem. Each air heating element usually consists of two substantially rectangular sheet m'etal plates which are arranged side by side and spaced apart and have .both of their end edges and one of their longitudinal edges closed, and

their other longitudinal edges closed except for inlet and outlet openings adjacent to their upper and lower ends, respectively, for permitting the air to be heated to pass between an theplates'.

An object of the present invention is to increase the efficiency of air heaters of the character indicated.

Another objectof the invention is to rovide an air heater of this character w ich is simple in construction, and in which the maximum area of heat radiating surface is employed.

The several features, of. the invention, whereby the above'me'ntioned and other ob jects maybe attained, will be clearly understood from the following description and accompanying drawings, in which:

Figure 1 is a side elevation, partlybroken away, of an air heating element constituting a component part of m improved air heater; Fig. 2-is a sectiona fview on an enlarged scale taken on the line 22 of Fig. 1 and as arranged in the air heater;

Fig. 3 is a sectional view on an enlarged 7 is a front view on a reduced scale one of the longitudinal edges 22 o showing ,aplurality. of air heating elements Y 1925. Serial No. 28,878.

The air heater as illustrated in i of v the drawings is provided with a casing 2 having its lower end adapted to be in communication with a furnace flueithrough a conduit 4 and its upper end adapted to be in communication with a chimney flue through a conduit 6 so as to cause the waste gases of combustion from the furnace to pass therethrough. The interior of the casing is divided vertically into opposed air heating chambers 8 each having an air inlet 10 and an air outlet 12. The chambers 8 are arranged at opposite sides of a vertical flue 14 which 1s An air heating section is arranged in each of the chambers 8 and is made up of a plurality of air heating elements arranged side by side and spaced apart so as to provide gas passes between themthat extend between the inlet and outlet conduits 4 and 6 of the heater casing. Each of the air heating elements is made up of two substantiall rectangular sheet metal plates 18 arrange side by side and spaced apart to provide an air passageway theplates apted to be controlled by a damper 16.

tween them. The end edges 20 and'- of each air heating element are brought to--- gether so as to close these edges, and the cen-" tral portion 24 of the other longitudinal edges of the plates are brought together so as to close that edge portion. The portions of the latter longitudinal edges of the plates extendin between the portion 24 and the ends of t e plates are bent outwardly so as to form inlet and outletopgnings 26 and 28, respectively. The space tween the plates is ivided u into a plurality of passa es which have t eir ends extendin to the in ct and outlet openings 26 and 28 y means of suitably shaped angle irons 30 arranged between the plates and welded to at least one of them, each angle iron having horizontal end ortions'29 and a vertical central portion 31.

n assembling the air "heating elements, as above described, a series of vertically ar- Y ranged angle irons 32 are placed between the elements so as to space them apart, the out wardly bent edge portions ofthe walls of the inlet and outlet openings 26 and 28 of adglaoent elements being we ded together as in 'cated in Fig. 2. The air heating elements are so positioned in the heater casing that I the inlet and outlet openings 26 and 28 of each air heating section are in communication with the associated air inlet and outlet and 12, res tively.

xcept as above referred to may be of a well-known construction.

In accordance with the present invention, the construction is such that a maximum area of heating surfaces is provided, and this is done without causing any material decrease in the rate of the passage of the air through the air heating elements or in the passage of the waste gases through the gas passes. To provide for this in accordance with the form of my invention illustrated in Figs. 1, 2 and 3 of the drawings, a series of two spirally twisted strips 34 are arranged side by side in each air passage formed by the angle irons 30, the s iral strips extending substantially the lengt of the vertical central portions 31 of the adjacent angle irons. Also as shown in these figures, the lates of the heating elements are provided with corrugations 38 which are suitably formed so as to closely surround opposite longitudinal ortions of the twisted strips 34.- With this construction it will be apparent that the air passing through the assages in each air heating eleinent will be roken up and will be caused to travel in more or less spiral paths therethrough as the air passes over the twisted strips 34. Thus the twisted strips 34 and the corrugations 38 add materially to the air heating surfaces of the heatin elements andthus ater eficienc in the heating of the air will be secured. t will also be apparent that such a construction will not materially retard the flow of the streams of air throng the passages. In the construction illustrated in Fig. 6 a series of twisted stri s 40 are arranged longi- "tudinally .between the heating elements and may if desired extend substantially the length stri s 40 will also have the effect of incre e area of the heat radiating surfaces of t e elements and this will be done without materially retarding the flow of the waste gases through the space between the elements.

'In the form illustrated in Fig. 4 the plates of each air heatin element are flat, and the increased heat ra 1ating surface is obtained by the mere positioning of twisted metal strips 42 in the air passages of the heating element.

The form illustrated in Fig. 5 is the-same as that illustrated in Fig. 4 except that twisted metal strips 44 are arranged in the 06 gas passes between the heating elements.

hereinafter described, the parts I of the lates. It will be apparent that these twister? The twisted strips in both the air passa and the gas passes may be held in position y s ot-welding them to one of the adjacent p ates.

As will be evident to those skilled in the art, my invention permits various modifications without departing from the spirit thereof or the scope of the appended claims.

What I claim is:

1. An air heating element for an air heater of the class described having, in combination, two plates arranged side by side and spaced apart, a plurality of partitions arranged in parallel relation between the plates to provide a plurality of air passages, and devices arranged in said airpassages tending to cause: a part of the air passing through each of said passages to traverse a spiral path, opposite sides of each of said devices being arranged closely adjacent to said plates, and the air passing between the plates being heated by the application of heat to the outer surfaces of the plates.

2. An air heating element for an air heater of the class described having, in combination. two plates arranged side by side and spaced apart, a plurality of partitions arranged in parallel relation between the plates to provide a plurality of air passages and devices arranged in said air passages tending to cause a part of the air passing through each of said passa es to traverse a spiral path, comprising spirally twisted strips arranged longitudinally in said passages, opposite sides of each of said strips being arranged closely adjacent tosaid plates, and the air passing between the plates being heatedby the application of heat to the outer surfaces of the plates.

3. An air heating element for an air heater of the class described having, in combination. two plates arranged side by side and spaced apart to (provide an air passageway between them, an devices arranged in said air passagewa tending to cause air passing therethroug to traverse a plurality of substan-. tially, spiral longitudinally extending paths. comprising -a urality of s irally twisted, strips arran longitudinal y in the general direction of the assa e of the air, said plates having a lura ity o corrugations extendin longitu inally thereof and suitably forme to cause the material of the plates to closely surround opposite longitudinal portions of said strips, and the air assing between the plates being heated by t e application of heat to the outer surfaces of the plates.

In testimony whereof, I have signed my name to this specification this 6th day of May,

VIRGINIUS 'Z. CARACRISTI. 

